The FBI has requested to hold an interview with the informant whose complaint led to the political trial against the president, Donald Trump, in the House of Representatives, a source directly familiar with the matter told NBC News.
However, that informant, whose identity has not been made public, has not yet agreed to grant an interview, the source said.
The FBI request was first reported by Yahoo! News, which said some officials at this agency were upset that the Justice Department refused to investigate the complainant's complaint about President Trump's handling of Ukraine after the Inspector General of the Intelligence Community referred it as a criminal case.RELATED
FBI spokesmen and the Department of Justice did not immediately respond to requests for comment from NBC News.
Justice Department officials said they examined the crime referral against Trump based on that person's complaint and decided that no investigation should be conducted. They also said they only examined whether a campaign financing offense occurred, but never explained why they did not consider bribery, extortion or other possible crimes.
The complainant was not present in the call that took place last July 25 between President Donald Trump and his Ukrainian counterpart, so he is not considered a first-hand witness to any of the key moments in the Ukraine case.
The informant increased the concerns conveyed by other colleagues in the National Security Council, and included them in a written complaint that he sent to the inspector general of the intelligence community.
Since he is not considered a first-hand witness, Democrats in Congress have decided that they do not need the complainant's testimony at the current political trial hearings.
For their part, Republicans have urged him to come forward to testify, something his critics consider as an attempt to expose the identity of this person.